1. Technical Field
The present invention relates to an electric power generation method using solar cells and a photovoltaic power generation system, and more particularly to an electric power generation method using solar cells and a photovoltaic power generation system suitable to use radiation emitted from radioactive waste that is generated by reprocessing spent nuclear fuel, for power generation.
2. Background Art
The photoelectric power generation systems are known as the solar electric power generation systems. These solar electric power generation systems are provided with solar cells that convert energy in the visible light region (400 to 800 nm), which is part of optical energy released from the sun, into electric power.
An alpha-ray irradiation solar cell that uses radiation emitted from a radiation source (Co-60) is known as one kind of solar power generation system (see Japanese Patent Laid-open No. 2002-341094). In alpha-ray irradiation solar cell, a phosphor film is formed on a top surface of a solar cell, a plutonium 238 layer is formed on the phosphor film, and then a transparent conductive film and glass substrate are formed in that order on the plutonium 238 layer. When X-rays are injected through the glass substrate, the solar cell generates electric power. The use of the fluorescent material increases electromotive force.
It is also described that radiation (beta-rays and gamma-rays) emitted from Co-60 is applied to the alpha-ray irradiation solar cell. When these radiation are injected on the plutonium 238 layer, more alpha rays are generated in the plutonium 238 layer and thereby fluorescence emission by the fluorescent material is increased. As a consequence, the electric power generated in the solar cells increases.
Japanese Patent Laid-open No. 7(1995)-274417 discloses an electric power supply system in a micro machine that internally inspects heat exchanger tubes in a condenser. A phosphor layer is formed on an inner surface of the heat exchanger tube. A surface of a main body of the micro machine is covered with a photovoltaic device. Radiation is injected from an outside of the heat exchange tube to the phosphor layer, and fluorescence is emitted from the phosphor layer. The emitted fluorescence is injected into the photovoltaic device, causing the photovoltaic device to generate electric power. The generated electric power is supplied to internal circuits of the micro machine.
Characteristics of calcium tungsten oxide (CaWO4) and gadolinium oxysulfide activated by terbium (Gd2O2S:Tb), which are fluorescent materials, are described in Intensifying Screen and Fluorescent Screen, Kasei Optonix, Ltd. Sep. 2001, pages 17 and 18.
The energy spectrum of visible light from the sun and the sensitive wavelength region in an amorphous silicon solar cell and single crystalline silicon solar cell are described respectively in Chion No. 31, Principle of Electric Power Generation by Solar Cell and its Types and Characteristics, University of Tsukuba, Masataka Ito, No. 45, 2009.